To Spare a Rod
by Lady Horizon94
Summary: It's not easy to be an eldest son of the brilliant Royal Scientist... Especially in a world of "Kill or to be Killed. Underfell AU WARNING: DEALS WITH CHILD ABUSE


**A/N: So, I got this idea suddenly and I just had to write it. ^^ Basically this is how I view Underfell Dadster would be. WARNING: THIS WORK DEALS WITH CHILD ABUSE AND NEGLECT. IF THESE THINGS TRIGGER YOU PLEASE DO NOT READ.**

 **To Spare a Rod**

Simple, white room is suffocating hot and the air inside is stuffy making it hard for Sans to breath or even think. Sweat is dripping from his skull and neat clothes – black straight pants and white dress shirt - are sticky feeling like they are glued to the child's bones.

He's _so_ tempted to just open the large window next to him but he knows it wouldn't help – this is Hotland after all. The silhouette of the Core rises on the horizon dark and almost threatening. Sans knows it offers energy to everyone in the Underground, he knows it's the most important work in their dark system of caverns called home, but something about it unnerves him, makes shivers creep along his spine every time he lands his eyes on it.

Or perhaps it's because _it's his father's invention_ that makes it so unsettling.

Sans lifts his gaze from a small notebook to take a look at his father, the most powerful man in the Underground after Asgore. The brilliant man behind the core and the royal scientist.

W. D. Gaster.

He's tall, much taller than Sans ever will be. He walks slowly, without a sound holding a book with one hand. His long, spider like phalanges are elegant. In his other hand, he carries a cane. Just seeing it makes the child's soul quiver and pulse restlessly. It's long and black and present in every lesson even though Sans always hopes – _prays_ – that Gaster would have forgotten it. (He doesn't. Gaster never forgets anything.) The man has two cracks on his face which only makes him more intimidating. The boy has never asked where they came from – not after Papyrus got slapped after being too nosy about it.

White, long lab coat is always neat and it never has a stain on it. It only highlights Gaster's height and makes his bones look more pale. Glasses are lining his dark eyes, which never betray any emotion and it's terrifying since there's no telling when father is angry or satisfied.

Sans wishes there would be a clock, he has no idea how many minutes he has to sit in this boiling room. All he can do is look at the green board in front of him and try not to doze. The small skeleton is so tired despite his discomfort and all he wants to do is just close his eyes for a moment –

But Sans wouldn't _dare,_ not really. He doesn't even want to think about what father would do, what kind of punishment would await him.

It's funny. It almost feels like some kind of sick prank the universe has planned for him. There was a time Sans would have done anything to get Gaster's approval, to get him _notice_ him. Now, he tries to be invisible, to blend in the background whenever those cold eyes are examining him.

Before, the boy had been a disappointment. A weak older brother with one HP. Someone with no room in the world of kill or be killed. Sans had been a stain of their family. Unlike strong, tall Papyrus who had gained his first LV at the age of five.

Things took a drastic turn when Sans started to read his father's books – secretly of course. He had been sucked into the world of science and he even started to make his own theories at a very young age. Nothing big really, just small assumptions and thoughts.

Then, one day, Gaster caught him. Sans had waited to get punished, but instead, father had stared Sans like he was _seeing_ his own son for the first time. Day by day, Sans could feel that gaze, unsettling and heavy. Like he was an exotic animal from a zoo.

Gaster started homeschooling him. At first there had been excitement and eagerness. _Finally_ attention. _Finally_ recognition. The happiness was short lived when Sans learned exactly what spending time with his father meant. It didn't mean pats on the head and approving smiles. What it meant was bruises on his phalanges, dark, narrow closet and Papyrus's icy stares. No more running around in Waterfall, watching water swirl and whirl in a soothing manner and admiring broken crystals on the ceiling.

Sans is not allowed to go outside anymore. Gaster keeps him locked away only explanation being older son's fragile health. (Which wasn't his concern before all this)

The lessons are long, and it's spooky, how Gaster can go to his work after them – sometimes he brings Sans to Hotland giving him lessons at any moment he has free time. Like today.

It's getting harder to stay awake. Father's voice is low and slow floating in the room like a weird lullaby. If only the lesson ended soon, stars let it end soon –

Sans catches something in the corner of his eyes. He turns to look outside the window and sees three monster children. One of them has horns and wings which are a bit teared. The other one is big, catlike creature. There's menacing grin on both of their faces as they push and kick a small lizard monster around who is already full of scratches and wounds.

Sans is envious. It's terrible and twisted but _he is._ There's nausea inside his soul and of course he feels sympathy for the little monster but **_at least they are outside._**

The feeling passes quickly however. It's not as merry outside as the skeleton remembers, he knows this. No one dared to attack him because of reputation of his father but seeing dust piles and monsters tearing each other into pieces always made something squirm inside him –

"Care to answer my question, Sans?" The low, silent and threatening voice asks _just in front of Sans._ Every inch of the child's body tenses and he feels his breath get caught somewhere in his throat. He really doesn't want to turn to look at Gaster.

 _He hasn't been listening. He hasn't been listening and father would know._

Slowly, painfully so, Sans finally turns to meet the man's eyes. They look down at him expecting any kind of answer. The boy digs his memory desperately, trying to memorize _anything_ that would save him from the situation, but his thoughts are falling apart, running away in panic. Sans's gaze wander to look at the cane. Gaster has situated it to lean on his shoulder as he holds it. It stretches towards the ceiling looking much longer than before. Its' black, painted surface gleams softly in the light.

There's an almost minute of silence as the royal scientist waits. It could be called almost merciful. When time goes by and Sans only sweats more, Gaster swings his cane so it hits the floor with a sharp noise. Sans startles and even though last time he _promised_ himself, he wouldn't tremble he can't help it.

Gaster's face is as unreadable as ever. "I see", the man mutters deceptively gently which is bad. Sans has learned to fear that tone. Oh, why didn't he just _listen –_

"Hands on the table", his father orders coldly. The cane seems only grow, Sans could _swear_ it was shorter just a minute ago…

"Father – " Sans starts with a quivering voice. The bruises on his phalanges are not yet fully healed and they still ache time to time.

Gaster pushes his glasses so they are sitting better on his face. His mouth forms a cold line. " _Hands on the table, Sans_." There's no escape.

The boy's movements are painfully unwilling and slow. He can already feel the sharp pain ghosting over his hands. He wished he would have answered _at least_ something. Father is never as harsh when Sans answers wrong, doesn't hit nearly as hard. Gaster has once said mistakes are lamentable but at least they can teach something – but father absolutely _hates_ if Sans doesn't listen or if he doesn't know the answer.

Sans' bones start to rattle and he tries to keep his tears from falling. Father loathes any kind of weaknesses and they only lead to a bigger kind of punishment. Sans is really getting tired of that closet and he would like to eat his dinner tonight –

 _Smack,_ pain burns trough his phalanges and it's so hard to keep quiet, not letting sounds of distress getting slip from him. The ugly sound resonates through his earholes afterwards and he inhales. _One hit left…_

The other one is harder than the first one and for a moment Sans fears that part of his phalanges falls off.

As soon as the punishment is over, Sans withdraws his hands under the table, out of the cane's reach. Gaster looks at him disapprovingly letting out of small scoff.

"Let us continue – and Sans, _do_ pay attention this time. This is my best cane, and I would not like to let it wear off just because of you." The warning is like a bucket of icy water on the child leaving Sans cold all over – though he doubts that cane would wear off. More likely it's making his bones wear off.

"Yes, Father", Sans whispers submitting to his fate. Quietly in his mind Sans wishes that he would have never picked up Gaster's books or started to read them. He wishes there was some sort of entity who could turn back time and make this all better…

…But nobody came.


End file.
